| 1. |
- Mangles, SPD, et al.
(författare)
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Effect of contrast ratio on electron beam stability in laser wakefield acceleration experiments
- 2006
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Ingår i: Plasma Physics and Controlled Fusion. - 0741-3335. ; 48:12B, s. 83-90
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Tidskriftsartikel (refereegranskat)abstract
- Laser wakefield accelerators offer the possibility of compact electron acceleration. However one of the key outstanding issues with the results reported to date is the electron beam stability. Experiments on two laser systems reveal that the contrast ratio between the ASE pedestal and main pulse is an important factor in determining the quality of the electron beam. With a high contrast ratio (10^8) the electron beam profile is a well collimated single beam having a low pointing instability (<10 mrad rms). With a lower contrast (10^6) the beam profile contains multiple beamlets which exhibit a large pointing instability (~50 mrad rms). Ahigh contrast ratio not only improves the beam pointing stability (~6 mrad) but also stabilizes the electron beam energy reproducibility (5%).
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| 2. |
- Mangles, SPD, et al.
(författare)
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Laser-wakefield acceleration of monoenergetic electron beams in the first plasma-wave period
- 2006
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Ingår i: Physical Review Letters. - 1079-7114. ; 96:21
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Tidskriftsartikel (refereegranskat)abstract
- Beam profile measurements of laser-wakefield accelerated electron bunches reveal that in the monoenergetic regime the electrons are injected and accelerated at the back of the first period of the plasma wave. With pulse durations c tau >=lambda(p), we observe an elliptical beam profile with the axis of the ellipse parallel to the axis of the laser polarization. This increase in divergence in the laser polarization direction indicates that the electrons are accelerated within the laser pulse. Reducing the plasma density (decreasing c tau/lambda(p)) leads to a beam profile with less ellipticity, implying that the self-injection occurs at the rear of the first period of the plasma wave. This also demonstrates that the electron bunches are less than a plasma wavelength long, i.e., have a duration < 25 fs. This interpretation is supported by 3D particle-in-cell simulations.
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| 3. |
- Mangles, S. P. D., et al.
(författare)
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On the stability of laser wakefield electron accelerators in the monoenergetic regime
- 2007
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- The effects of plasma density and laser energy on the stability of laser produced monoenergetic electron beams are investigated. Fluctuations in the principal beam parameters, namely, electron energy, energy-spread, charge, and pointing, are demonstrated to be minimized at low densities. This improvement in stability is attributed to the reduced time for pulse evolution required before self-injection occurs; i.e., that the pulse is closest to the matched conditions for these densities. It is also observed that electrons are only consistently produced above a density-dependent energy threshold. These observations are consistent with there being a threshold intensity (a(0)greater than or similar to 3) required for the occurrence of self-injection after accounting for pulse compression. (C) 2007 American Institute of Physics.
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